Emerging Trends, Opportunities and Bottlenecks in Metal-based Advanced Oxidation Processes

<jats:p>In recent years, considerable attention in environmental remediation has been directed toward advanced oxidation processes (AOPs) for their adaptability and efficiency in degrading recalcitrant and emerging organic compounds, such as pharmaceuticals and pesticides. Among the various materials investigated, metal-based catalysts have drawn significant interest due to their chemical stability, catalytic efficiency, and cost-effectiveness. Metal-based catalysts feature dual active sites, metals as electron-deficient sites and heteroatoms as electron-rich sites, enabling continuous regeneration through redox reactions. This makes them effective for activating oxidants like persulfate, H2O2, and O3, producing reactive species via radical (˙OH, SO4˙−, O2˙−) and non-radical (¹O2, surface complexes, high-valent metals, electron transfer) pathways. Despite their high efficiency, metal-based catalysts in AOPs face challenges such as metal leaching, leading to secondary pollution and decreased catalytic stability, activity, and reusability. This underscores the need for improved immobilization methods and more stable catalyst designs. This chapter reviews recent advances in metal-based catalysts, including transition metals, metal oxides, nanoparticles, and metal–organic frameworks (MOFs) for water remediation. It discusses key issues like catalyst instability, metal leaching, and regeneration costs that limit long-term application. Emerging trends and future opportunities are highlighted, focusing on optimizing catalyst design to enhance activity, stability, and reusability while minimizing environmental risks. The article concludes by outlining sustainable and scalable strategies for advancing water treatment technologies.</jats:p>